Dynamic microvilli sculpt bristles at nanometric scale

Organisms generate shapes across size scales. Whereas patterning and morphogenesis of macroscopic tissues has been extensively studied, the principles underlying the formation of micrometric and submicrometric structures remain largely enigmatic. Individual cells of polychaete annelids, so-called chaetoblasts, are associated with the generation of chitinous bristles of highly stereotypic geometry. Here we show that bristle formation requires a chitin-producing enzyme specifically expressed in the chaetoblasts. Chaetoblasts exhibit dynamic cell surfaces with stereotypical patterns of actin-rich microvilli. These microvilli can be matched with internal and external structures of bristles reconstructed from serial block-face electron micrographs. Individual chitin teeth are deposited by microvilli in an extension-disassembly cycle resembling a biological 3D printer. Consistently, pharmacological interference with actin dynamics leads to defects in tooth formation. Our study reveals that both material and shape of bristles are encoded by the same cell, and that microvilli play a role in micro- to submicrometric sculpting of biomaterials.


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No sample was excluded from the data All attempts of replication was successful.Experiments were replicated within 1-3 years from the first pioneer experiment, except the SEM analyses of the bristle morphology that were unique but supported by alternative similar experiment performed by light microscopy.
Polychaete animals (Platynereis dumerilii) of the PIN and VIO strains were randomly mated, and developing larvae were randomly collected and processed.
The quantifications and phenotype comparisons were performed upon blinding.
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